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Mineral Resources > Online Spatial Data > Geology > by state > Colorado Geology

Geologic units in Conejos county, Colorado

[Additional scientific data in this geographic area]

Landslide deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers 2 % of this area

Locally includes talus, rock-glacier, and thick colluvial deposits

Lithology: landslide; talus; colluvium

Older gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 1 % of this area

Includes Slocum, Verdos, Rocky Flats, and Nussbaum Alluviums in east, and Florida, Bridgetimber, and Bayfield Gravels in southwest

Lithology: gravel; alluvium

Dakota, Burro Canyon, Morrison, and Wanakah Fms (Phanerozoic | Mesozoic | Jurassic Cretaceous) at surface, covers < 0.1 % of this area

Lithology: sandstone; mudstone; limestone

silicic pyroclastic rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lower Oligocene silicic pyroclastic rocks (ash-flow tuffs); includes Hell's Mesa, Kneeling Nun, lower part of Bell Top Formation, Caballo Blanco, Datil Well, Leyba Well, Rock House Canyon, Blue Canyon, Sugarlump and Tadpole Ridge Tuffs, the tuffs of the Organ cauldron, Treasure Mountain Tuff (now known as Chiquito Peak Tuff), Bluff Creek Tuff, Oak Creek Tuff, tuff of Steins Mountain, tuff of Black Bill Canyon, tuff of Farr Ranch, Woodhaul Canyon, Gillespie and Box Canyon Tuffs, Cooney Tuff, and other volcanic and interbedded fluvial and pumiceous units; (31-36.5 Ma)

Lithology: pyroclastic; tuff; felsic volcanic rock; volcanic rock (aphanitic); mixed clastic/volcanic

Intra-ash flow quartz latitic lavas (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.3 % of this area

Lithology: quartz latite

Older glacial drift (Phanerozoic | Cenozoic | Quaternary) at surface, covers 1 % of this area

Lithology: glacial drift

Modern alluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers 2 % of this area

Includes Piney Creek Alluvium and younger deposits

Lithology: alluvium

Granitic rocks of 1700-m.y. age group (Proterozoic | Paleoproterozoic) at surface, covers < 0.1 % of this area

Includes Boulder Creek -M.Y. AGE GROUP (AGE 1650-1730 M.Y.)--Includes Boulder Creek, Cross Creek, Denny Creek, Kroenke, Browns Pass, Powderhorn, Pitts Meadow, Bakers Bridge, and Tenmile Granites, Quartz Monzonites, or Granodiorites;

Lithology: granite; granodiorite; quartz monzonite

Eocene prevolcanic sedimentary rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

South-central: Arkosic sand and bouldery gravel of Echo Park Alluvium. Southwest: includes Telluride Conglomerate and Blanco Basin Fm (arkosic mudstone, sandstone, and conglomerate)

Lithology: sandstone; conglomerate; mudstone

sedimentary units, Palogene (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Paleogene sedimentary units; includes Baca, Galisteo, El Rito, Blanco Basin, Love Ranch, Lobo, Sanders Canyon, Skunk Ranch, Timberlake, and Cub Mountain Formations

Lithology: medium-grained mixed clastic; tuff; limestone; sand; clay or mud

landslide deposits and colluvium (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Landslide deposits and colluvium

Lithology: landslide; colluvium

Los Pinos Fm (Phanerozoic | Cenozoic | Tertiary) at surface, covers 7 % of this area

Volcaniclastic conglomerate interbedded with basalt flows of Hinsdale Fm (Tbb) on east flank of San Juan Mountains. Grades laterally into Santa Fe Fm of San Luis Valley

Lithology: mixed clastic/volcanic; basalt

Basalt flows (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Lithology: basalt

piedmont alluvial deposits (Phanerozoic | Cenozoic | Quaternary) at surface, covers < 0.1 % of this area

Piedmont alluvial deposits: upper and middle Quaternary; includes deposits of higher gradient tributaries bordering major stream valleys, alluvial veneers of the piedmont slope, and alluvial fans

Lithology: alluvium

Glacial drift (Phanerozoic | Cenozoic | Quaternary) at surface, covers 0.2 % of this area

Includes some unclassified glacial deposits

Lithology: glacial drift

Rhyolitic intrusive rocks and flows of late-volcanic bimodal suite (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lithology: rhyolite

Unclassified surficial deposits and underlying Alamosa Fm in San Luis Valley (Phanerozoic | Cenozoic | Tertiary Quaternary) at surface, covers 28 % of this area

Alamosa Fm: gravel, sand, silt

Lithology: alluvium

Pre-ash-flow andesitic lavas, breccias, tuffs, and conglomerates (Phanerozoic | Cenozoic | Tertiary) at surface, covers 19 % of this area

Includes several named units

Lithology: andesite; tuff; volcanic breccia (agglomerate)

Gravels and alluviums (Phanerozoic | Cenozoic | Quaternary) at surface, covers 2 % of this area

Includes Broadway and Louviers Alluviums

Lithology: gravel; alluvium

Mancos Shale (Phanerozoic | Mesozoic | Cretaceous) at surface, covers < 0.1 % of this area

In northwest and west-central: Intertongues complexly with units of overlying Mesaverde Group or Fm; lower part consists of a calcareous Niobrara equivalent and Frontier Sandstone and Mowry Shale Members; in areas where the Frontie

Lithology: shale; sandstone

Intra-ash flow andesitic lavas (Phanerozoic | Cenozoic | Tertiary) at surface, covers 3 % of this area

Lithology: andesite

Basalt flows and associated tuff, breccia, and conglomerate of late-volcanic bimodal suite (Phanerozoic | Cenozoic | Tertiary) at surface, covers 15 % of this area

Includes basalts of Hinsdale Fm in San Juan Mountains - Servilleta Fm in San Luis Valley and many other occurrences

Lithology: basalt; tuff; volcanic breccia (agglomerate); conglomerate

Ash-flow tuff of main volcanic sequence (Phanerozoic | Cenozoic | Tertiary) at surface, covers 19 % of this area

Includes many named units

Lithology: ash-flow tuff

volcanic rocks, lower Oligocene and Eocene (Phanerozoic | Cenozoic | Tertiary) at surface, covers < 0.1 % of this area

Lower Oligocene and Eocene volcanic rocks, undifferentiated; dominantly intermediate composition, with interbedded volcaniclastic rocks; (31-44 Ma)

Lithology: volcanic rock (aphanitic); intermediate volcanic rock; mixed clastic/volcanic

Middle Tertiary intrusive rocks (Phanerozoic | Cenozoic | Tertiary) at surface, covers 0.9 % of this area

Intermediate to felsic compositions

Lithology: plutonic rock (phanerit